This invention relates to the field of the internal combustion engines.
The prior art is a four-cycle engine with oil lubrication, the oil being separately stored from the fuel. The oil is purposefully delivered to the corresponding lubrication points, or it comes from an oil sump as an oil-air mixture (oil mist) to the lubrication points.
The lubrication of a four-cycle internal combustion engine with a fuel-oil-air mixture, similar to the lubrication of two-cycle engines, is also known. The mixture is guided by the carburetor into the crank chamber. A one-way valve avoids the flowing back of the mixture into the carburetor. The mixture arrives over a tubular duct directly into the cylinder head or into a compression chamber. A further one-way valve avoids then the flowing back of the mixture into the crank chamber (see for example the printed document EP-A1-0 631040).
In the known mixture lubrication of the four-cycle internal combustion engine, the whole mixture is guided through the crank chamber to the intake port. This does not only cause an undesired increased flow resistance but also makes necessary the complicated and expensive installation of different valves at different points. A further disadvantage is that the whole mixture is heated through the crank chamber and that the filling of the cylinder is thus reduced.
The aim of the invention is thus to create a four-cycle internal combustion engine with mixture lubrication which is simply structured for a lubrication which is simultaneously independent of the position and which has a favourable behaviour with respect to the mixture charge.
The aim is achieved by the characteristics of the present invention, taken as a whole. The core of the invention consists in guiding only one part of the mixture for lubrication through the crank chamber, while the other part directly arrives from the carburetor through the intake port into the combustion chamber.
A first preferred embodiment of the engine according to the invention is characterized in that the carburetor is directly connected with the intake port and that the means comprise an overflow duct which leads from the intake port to an overflow opening on the crankcase and, controlled by valve means, connects the intake port with the crank chamber. With this arrangement, a very efficient filling of the combustion space with a mixture can be achieved because of the short paths between the carburetor and the intake port.
A second alternative embodiment is characterized in that the means comprise an overflow duct which leads from the intake port to an overflow opening on the crankcase and, controlled by valve means, connects the intake port with the crank chamber and that the carburetor is connected with the overflow duct or the overflow opening by the valve means. This arrangement makes possible in particular the control of the whole mixture flow through the valve means.
Another preferred embodiment of the engine according to the invention is characterized in that the valve means comprise a rotary disk valve. Such a rotary disk valve makes possible a particularly precisely controlled charge of the mixture part flowing by the crank chamber.
A preferred further development of this embodiment is characterized in that the rotary disk valve is placed in the crankcase at the overflow opening and periodically opens and closes this opening and that the rotary disk valve is driven by a camshaft which actuates the admission and exhaust valves over taper push rods and which is in particular integrated into the camshaft, A space saving arrangement and a simplified drive of the rotary disk valve is thus made possible.